The present disclosure is related to air filtering systems having non-cylindrical filter elements, and methods of using systems equipped with non-cylindrical filter elements.
Many industries often encounter particulate matter suspended in the atmosphere. In some industries, this particulate matter is a valuable product, for example, starch; it would be beneficial if these suspended particulate could be recovered and reintroduced into the process. For other industries, such as metal or wood working, the particulate matter may be simply dust; it is desirable to remove dust particles from the air in order to provide a clear working environment.
Systems for cleaning an air or other gas stream laden with particulate matter include air filter assemblies that have filter elements disposed in a housing. The filter element may be a bag or sock of a suitable fabric or pleated paper. The gas stream, contaminated with particulate, typically is passed through the housing so that the particulate are captured and retained by the filter element. Cleaning is accomplished by periodically pulsing a brief jet of pressurized air into the interior of the filter element to reverse the air flow through the filter element, causing the collected contaminants to be collected . Such air filter assemblies are disclosed in, for example, U.S. Pat. No. 4,218,227 (Frey) and U.S. Pat. No. 4,395,269 (Schuler), which patents are hereby incorporated by reference.
Cylindrical filter elements are usually used in an air filter assembly to process dust particles from an airstream. In a standard design of air filter assembly, an air filter assembly has a clean air chamber and a dirty air chamber. The two chambers are separated by a sheet metal, commonly referred to as a tube sheet. The tube sheet has a number of openings from which cylindrical filters are aligned. The filters suspend downwardly with or without an angle from the tube sheet openings into the dirty air chamber. Particulate-laden air is introduced into the dirty air chamber, and the particulates collect onto the filter. The filtered air passes through the filters to the interior of the filters, and upwardly out through the openings in the tube sheet into the clean air chamber. From the clean air chamber, the cleaned air is exhausted into the environment, or recirculated for other uses. For example, U.S. Pat. Nos. 4,424,070 (Robinson), U.S Pat. No. 4,436,536 (Robinson), U.S Pat. No. 4,443,237 (Ulvestad), U.S Pat. No. 4,445,915 (Robinson), U.S Pat. No. 5,207,812 (Tronto et al.), U.S Pat. No. 4,954,255 (Muller et al.), U.S Pat. No. 5,222,488 (Forsgren), and U.S Pat. No. 5,211,846 (Kott et al.) are prior art examples of prior art cylindrical filter elements of the pleated cartridge type.
Non-cylindrical filter elements are sometimes used to process dust, particles from an airstream and provide increased filtration area within a housing than cylindrical filter elements. For example, U.S. Pat. No. 5,730,766 (Clements) discloses a non-round unitary filter cartridge having a unitary structure with pleated filter media formed securely about a perforated interior core in a dust collector. U.S. Pat. No. 4,661,131 (Howeth) discloses non-cylindrical filters having a greater clean air flow area than a plurality of cylindrical elements fitted within the same dimensional envelope.
In one conventional design of air filter assembly with non-cylindrical filter elements, non-cylindrical filter elements simply replaces cylindrical filter elements. With less space between adjacent filter elements, more non-cylindrical filter elements are placed within a housing than cylindrical filter elements. U.S. Pat. No. 5,730,766 (Clements) discloses this type of use of non-cylindrical filter elements.
In another conventional design of air filter assembly with non-cylindrical filter elements, a plurality of cylindrical elements are replaced by a single non-cylindrical filter element. U.S. Pat. No. 4,661,131 (Howeth) discloses this type of use of non-cylindrical filter elements.
Unfortunately, each of these conventional designs which utilize non-cylindrical filter elements has its disadvantages and drawbacks.
The construction and arrangement of the disclosed air filter assembly helps to overcome the problems of the prior art. In particular, in one embodiment, the structure and arrangement of the assembly of the present disclosure enables the processing of 25% more dust laden airflow compared to conventional systems. In preferred systems, the assembly of the present disclosure results in a dust laden airflow increase greater than 25% without an increase in the geometric size of the filter housing apparatus or the number of filter cartridges required. The present design provides this 25% volume increase, preferably greater than 25% increase, by maintaining the amount of filtration media available for filtering the dirty air rather than increasing the amount of filtration media. In another embodiment, the assembly of the present disclosure results in an airflow increase greater than 25% by decreasing the amount of filtration media available. Also, the structure and arrangement of the air filter assembly provides more efficient filter retention/sealing, filter housing apparatus manufacturing, and filter handling.
In one aspect, the disclosure describes an air filter assembly adapted for removing particulate matter from a high volume air stream. The air filter assembly of the present disclosure, utilizing non-cylindrical filter elements, is capable of handling 25% more air than a conventional air filter assembly utilizing cylindrical filter elements having the same amount, or less, surface area available for filtration. In particular, an air filter assembly of the present disclosure comprises a housing including an air inlet, an air outlet, and a spacer wall separating the housing into a filtering chamber and a clean air chamber, the spacer wall including a first air flow aperture therein. The air inlet provides a dirty air volume to the air filter assembly, where the dirty air volume has an air flow direction. The air filter assembly further includes a first filter construction positioned in air flow communication with the first air flow aperture in the spacer wall; the first filter construction including an extension of filter media disposed between proximal end cap and distal end cap. The filter media, proximal and distal end caps defines a filter construction inner clean air chamber. The first filter construction: is oriented within the filter inner clean air chamber in air flow communication with the spacer wall first air flow aperture; has a cross-sectional area, when taken parallel to the first air flow aperture, the cross-sectional area having a long axis perpendicular to a short axis; and has a width along the long axis and a width along the short axis, the long axis width being greater than the short axis width and the long axis positioned parallel to the air flow direction.
In another aspect or embodiment, an air filter assembly is provided that comprises a housing including an air inlet, an air outlet, a spacer wall separating said housing into a filtering chamber and a clean air chamber and including a first air flow aperture therein. The air inlet provides a dirty air volume to the air filter assembly, the dirty air volume having an air flow direction and an air speed. The air filter assembly further includes a first filter construction: positioned in air flow communication with the first air flow aperture in the spacer wall; including an extension of filter media defining a filter construction inner clean air chamber; having a cross-sectional area, when taken parallel to the first air flow aperture, the cross-sectional area having a long axis perpendicular to a short axis; having a width along the long axis and a width along the short axis, the long axis width being greater than the short axis width and the long axis positioned parallel to the air flow direction; and further having a first surface area defined by the extension of filter media. The volume of dirty air processable by this air filter assembly is at least 10 percent greater, preferably 20 percent greater, and most preferably at least 25 percent greater than a volume of dirty air processable by an air filter assembly differing from the claimed assembly only by the shape of the filter elements.
In another embodiment, the structure and arrangement of the assembly of the present disclosure results in an air speed that is at least 10 percent, preferably 20 percent, and most preferably at least 25 percent less than the air speed of a similar volume of air being filtered by an air filter assembly differing from the claims assembly only by the shape of the filter elements.
Such an air filter assembly provides for longer filter life and increases the capacity for particulate removal from the incoming dirty air stream, thus decreasing the need to change used filter elements.
In another aspect, such an air filter assembly provides greater capacity, both for the airflow capacity and the amount of particulate removed from the dirty air stream, without decreasing filter life. This decreases the total amount of filters needed at each replacement cycle and over the life of the operation.
A method of filtering or cleaning dirty air to provide clean air is also disclosed.